getHeadEdges

getHead

Returns the head dependency node if it exists, otherwise null. If there exists more
than one head the first head is returned according to the linear order of the terminals
or the root if it is one of the heads.

getHeadEdge

Returns the edge between the head and the node if it exists, otherwise null. If there exists more
than one head edge the first head edge is returned according to the linear order of the terminals
or the root if it is one of the heads.